This application claims the priority of German Application No. 100 18 719.6, filed Apr. 15, 2000, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a coupling element for connecting an electric apparatus to an optical data bus with a unidirectional transmission.
In the case of electrical apparatuses, which are connected to conventional optical data buses, an optical receiver (opt-in), as a component of an opto-electrical transducer, and an optical transmitter (opt-out), as a component of an electro-optical transducer, are situated in the interior of each apparatus. The two transducers are used for transmitting the data telegrams incoming from the data bus to the apparatus and for transmitting the outgoing data telegrams to the data bus.
For this purpose, one optical interface between the data bus and the electrical apparatus, respectively, must be implemented for each of the two transducers. This interface has to be designed using high-cost constructive measures to accommodate many plug-in cycles since the apparatuses must be frequently unplugged and plugged in again (service). In addition, this interface is susceptible to dirt and other environmental influences (chemicals, deposits . . . ). It must be protected by means of high-cost mechanical constructions.
It is another disadvantage that optical elements are placed in the interior of the electrical apparatuses. The optical system is sensitive to high temperatures generated in the interior of many apparatuses. The apparatuses must be cooled by high-cost measures (cooling constructions, fans . . . ) In addition, the optical elements are not equally suitable for automatic manufacturing processes. During the processing, high-cost and expensive special processes must be carried out. If the supply voltage of an apparatus fails or if the apparatus is not (or not correctly) plugged in, particularly in the case of optical ring buses, the entire bus is incapacitated because an incoming optical signal can no longer be transported to the user in the following bus.
It is an object of the present invention to provide a coupling element of the above-mentioned type, which is simple and robust with respect to its handling and which can be used particularly in a highly stressed environment. In particular, it should be suitable for a use in a motor vehicle.
The invention achieves this object by providing a coupling element for connecting an electrical apparatus to an optical data bus with a unidirectional transmission, characterized in that a housing contains an opto-electrical transducer to which an input data bus line is optically connected, and an electro-optical transducer to which an output data bus line is optically connected. Also, two electrical contacts are provided on the exterior side, by way of which the two transducers with the apparatus can be electrically connected. Further, a switchable electrical connection is provided between the two transducers which, when the apparatus is connected, is open and when the apparatus is not connected, is closed.
The optical elements, particularly the optical receiver and the optical transmitter are integrated in the coupling element. An xe2x80x9cactive optical coupling elementxe2x80x9d is created in this manner. If the coupling element is unplugged from the apparatus, the electric output signal of the opto-electrical transducer is guided directly onto the electro-optical transducer. If the coupling element is plugged to the apparatus, the electric connection of the two transducers is separated by way of the (mechanical or electronic) switch. The output signal of the opto-electrical transducer is guided into the apparatus for processing. The electric output signal of the apparatus is fed to the data bus by way of the electro-optical transducer.
The power supply of the two transducers advantageously takes place independently of whether the coupling element is arranged on the apparatus. The electrical connection lines therefor end, like the optical waveguides, in the coupling element. The elements which may be additionally required for the power supply of the two transducers, such as adapter elements, amplifiers, etc., can also be arranged in the coupling element. As a result, an integrated power supply system for the two transducers is obtained.
The power supply system can have separate connection contacts. Furthermore, when the coupling element is arranged, a power supply (for example, +12V and Gnd) can be represented by way of the coupling element for the apparatus.
The two data bus lines connected with the transducers can be non-detachably connected with the latter, for example, they may be cast-in. This further reduces the danger of contamination.
The electrical connection between the two transducers can be switched using a proximity switch which responds when the apparatus is present. Such proximity switches operate reliably and require little space and no additional electrical control connections.
Advantageously, the active optical coupling element additionally contains a signal processing unit which generates the output signal of the opto-electrical transducer such that an ideal pulse-pause ratio with a low pulse duration distortion is obtained.
Arbitrary exit angles of the optical cables can easily be implemented because the required bending can be implemented on the electrical side and thus with an arbitrarily small bending radius.
The invention increases the amount of security. The operation, even of a ring bus, is no longer interrupted by the unplugging of an apparatus because the signal is shortcircuited in the coupling element and the incoming optical signal is regenerated and forwarded to the apparatus which follows.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.